Polymer electrolyte membrane

ABSTRACT

The present specification relates to a polymer electrolyte membrane including a polymer and inorganic particles.

TECHNICAL FIELD

The present specification claims priority to and the benefits of Korean Patent Application Nos. 10-2014-0173157, 10-2014-0173178, 10-2014-0173137 and 10-2014-0173142 filed with the Korean Intellectual Property Office on Dec. 4, 2014, and Korean Patent Application No. 10-2015-0088929 filed with the Korean Intellectual Property Office on Jun. 23, 2015, the entire contents of which are incorporated herein by reference.

The present disclosure relates to a polymer electrolyte membrane.

BACKGROUND ART

A fuel cell is an energy conversion device directly converting chemical energy of fuel into electric energy. In other words, a fuel cell employs a power generation method utilizing a fuel gas and an oxidizer, and using electrons generated during the oxidation and reduction reactions thereof to produce power. A membrane-electrode assembly (MEA) of a fuel cell is a part where an electrochemical reaction of hydrogen and oxygen occurs, and is formed with a cathode, an anode and an electrolyte membrane, that is, an ion conductive electrolyte membrane.

A redox flow battery (oxidation-reduction flow battery) is a system charged and discharged by active materials included in a liquid electrolyte being oxidized and reduced, and is an electrochemical storage device directly storing chemical energy of the active materials as electric energy. A unit cell of the redox flow battery includes an electrode, an electrolyte and an ion-exchange membrane (electrolyte membrane).

Due to their high energy efficiency and environmental friendly properties of low contaminant emissions, fuel cells and redox flow batteries have been researched and developed as a next generation energy source.

A core constituent in a fuel cell and a redox flow battery is a polymer electrolyte membrane capable of cation exchange, and properties of 1) excellent proton conductivity, 2) preventing an electrolyte crossover, 3) high chemical resistance, 4) strengthening mechanical properties and/or 4) low swelling ratio are favorably required. The polymer electrolyte membrane is divided into fluorine-based, partial fluorine-based, hydrocarbon-based and the like, and, by having a fluorine-based main chain, the partial fluorine-based polymer electrolyte membrane has advantages of exhibiting excellent physical and chemical stability and high thermal stability. In addition, in the partial fluorine-based polymer electrolyte membrane, a cation transfer functional group is attached at the end of the fluorine-based chain as in the fluorine-based polymer electrolyte membrane, and therefore, advantages of both a hydrocarbon-based polymer electrolyte membrane and a fluorine-based polymer electrolyte membrane are capable of being obtained.

However, the partial fluorine-based polymer electrolyte membrane has a problem in that cation conductivity is relatively low since micro-phase separation and aggregation of a cation transfer functional group are not effectively controlled. Accordingly, researches have been progressed in the direction of securing high cation conductivity through controlling distribution and micro-phase separation of a sulfonic acid group.

PRIOR ART DOCUMENTS Patent Documents

Korean Patent Application Laid-Open Publication No. 2003-0076057

DISCLOSURE Technical Problem

The present specification is directed to providing a polymer electrolyte membrane readily obtaining phase separation and having excellent mechanical properties.

Technical Solution

One embodiment of the present specification provides a polymer electrolyte membrane including a polymer including a unit represented by the following Chemical Formula 1; and inorganic particles.

In Chemical Formula 1,

A is —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁻, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻2M⁺, —O(CF₂)_(n)SO₃H, —O(CF₂)_(n)SO₃ ⁻M⁺, —O(CF₂)_(n)COOH, —O(CF₂)_(n)COO⁻M⁺, —O(CF₂)_(n)PO₃H₂, —O(CF₂)_(n)PO₃H⁻M⁺ or —O(CF₂)_(n)PO₃ ²⁻2M⁺,

m is an integer of 2 to 6,

M is a group 1 element,

R1 and R2 are the same as or different from each other, and each independently a halogen group, and

n is an integer of 2 to 10, and structures in the 2 to 10 parentheses are the same as or different from each other.

Another embodiment of the present specification provides a membrane-electrode assembly including an anode; a cathode; and the polymer electrolyte membrane described above provided between the anode and the cathode.

Still another embodiment of the present specification provides a polymer electrolyte-type fuel cell including two or more of the membrane-electrode assemblies; a stack including a bipolar plate provided between the membrane-electrode assemblies; a fuel supplying unit supplying fuel to the stack; and an oxidizer supplying unit supplying an oxidizer to the stack.

Lastly, yet another embodiment of the present specification provides a redox flow battery including a positive electrode cell including a positive electrode and a positive electrode liquid electrolyte; a negative electrode cell including a negative electrode and a negative electrode liquid electrolyte; and the polymer electrolyte membrane described above provided between the positive electrode cell and the negative electrode cell.

Advantageous Effects

A polymer electrolyte membrane including a polymer according to one embodiment of the present specification readily forms a hydrophilic-hydrophobic phase separation structure.

In addition, by controlling the phase separation structure, the polymer electrolyte membrane efficiently forms a hydrophilic channel in the polymer electrolyte membrane.

The polymer electrolyte membrane according to one embodiment of the present specification has excellent proton conductivity. As a result, high performance of a fuel cell and/or a redox flow battery including the same is obtained.

By further including inorganic particles, the polymer electrolyte membrane according to one embodiment of the present specification is capable of preventing a swelling phenomenon caused by a solvent, and enhancement in mechanical properties and chemical stability can be expected.

In addition, a polymer electrolyte-type fuel cell including the polymer electrolyte membrane according to one embodiment of the present specification is capable of preventing a gas crossover, and enhancing ion conductivity even under a low humidity condition.

Additionally, a redox flow battery including the polymer electrolyte membrane according to one embodiment of the present specification is capable of preventing a vanadium ion crossover.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a principle of electricity generation of a fuel cell.

FIG. 2 is a diagram schematically illustrating one embodiment of a redox flow battery.

FIG. 3 is a diagram schematically illustrating one embodiment of a fuel cell.

FIG. 4 is an image measuring a surface of a film according to Example 2 using a scanning electron microscope (SEM).

REFERENCE NUMERAL

100: Electrolyte Membrane

200 a: Anode

200 b: Cathode

10, 20: Tank

11, 21: Pump

31: Electrolyte Membrane

32: Positive Electrode Cell

33: Negative Electrode Cell

41: Positive Electrode Liquid Electrolyte

42: Negative Electrode Liquid Electrolyte

60: Stack

70: Oxidizer Supplying Unit

80: Fuel Supplying Unit

81: Fuel Tank

82: Pump

MODE FOR DISCLOSURE

Hereinafter, the present specification will be described in more detail.

In the present specification, a description of a certain part “including” certain constituents means capable of further including other constituents, and does not exclude other constituents unless particularly stated on the contrary.

In the present specification, a ‘unit’ is a repeated structure of a monomer being included in a polymer, and means a structure of a monomer being bound in a polymer through polymerization.

In the present specification, the meaning of ‘including a unit’ means being included in a main chain in a polymer.

In the present specification, the “electrolyte membrane” is a membrane capable of exchanging ions, and includes a membrane, an ion-exchange membrane, an ion-transfer membrane, an ion-conductive membrane, a separator, an ion-exchange separator, an ion-transfer separator, an ion-conductive separator, an ion-exchange electrolyte membrane, an ion-transfer electrolyte membrane, an ion-conductive electrolyte membrane or the like.

One embodiment of the present specification provides a polymer electrolyte membrane including a polymer including a unit represented by Chemical Formula 1 and inorganic particles.

By including a polymer including a unit represented by Chemical Formula 1, the polymer electrolyte membrane according to one embodiment of the present specification has high mechanical strength and high ion conductivity, and phase separation of the electrolyte membrane may be readily obtained.

In addition, by including inorganic particles, the polymer electrolyte membrane according to one embodiment of the present specification prevents a swelling phenomenon caused by a solvent, and enhancement in mechanical properties and chemical stability may be expected.

In one embodiment of the present specification, the inorganic particles have a particle diameter of 5 nm to 50 μm. In one embodiment of the present specification, the inorganic particles more preferably have a particle diameter of 5 nm to 1000 nm.

When the inorganic particles have a particle diameter of less than 5 nm, dispersion of the inorganic particles is difficult in the polymer electrolyte membrane, and when the particle diameter is greater than 50 μm, the inorganic particles are difficult to be evenly dispersed in the polymer electrolyte membrane, which negatively affects enhancement in the polymer electrolyte membrane performance.

The inorganic particles according to one embodiment of the present specification may have a spherical shape.

In the present specification, the “particle diameter” means a diameter of a particle, and an average value of diameters of the widest section of particles.

In the present specification, the particle diameter of the inorganic particles is measured by dynamic light scattering.

In one embodiment of the present specification, the inorganic particles are one, two or more selected from the group consisting of inorganic matters, heteropolyacids and inorganic acids.

In the present specification, examples of the inorganic matter may include BaTiO₃, Pb(Zr_(x),Ti_(1-x))O₃ (PZT, 0<x<1), Pb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃ (PLZT, 0<x<1, 0<y<1), (1-x)Pb(Mg_(1/3)Nb_(2/3))O₃-xPbTiO₃ (PMN-PT, 0<x<1), hafnia (HfO₂), SrTiO₃, SnO₂, CeO₂, MgO, NiO, CaO, ZnO, ZnO₂, ZrO₂, SiO₂, Y₂O₃, Al₂O₃, SiC, TiO₂, tetraethyl orthosilicate (TEOS), montmorillonite (MMT), (P₂O₅)₄(ZrO₂)₃, P₂O₅—ZrO₂—SiO₂ and the like, but are not limited thereto.

Examples of the inorganic acid may include CsDSO₄, CsHSO₄ and the like, but are not limited thereto.

Examples of the heteropolyacid may include α-Zn (O₃PCH₂OH)_(1.27) (O₃PC₆H₄SO₃H)_(0.73)nH₂O, γ-Zr (PO₄) (H₂PO₄)_(0.54) (HO₃PC₆H₄SO₃H)_(0.46)nH₂O, Zr(O₃PCH₂OH)_(1.27)Y_(0.73)nH₂O, α-Zr (O₃PC₆H₄SO₃H)_(3.6)H₂O, α-Zr(O₃POH)H₂O, β-Cs₃ (HSO₄)₂(Hx (P, S)O₄), αCs₃(HSO₄)₂(H₂PO₄) phosphotungstic acid, silicotungstic acid, molybdophosphoric acid (H₃PO₄12MoO₃zH₂O) and the like, but are not limited thereto.

Specifically, as the inorganic particles in one embodiment of the present specification, one, two or more types may be selected from the group consisting of BaTiO₃, Pb(Zr_(x),Ti_(1-x)) O₃ (PZT, 0<x<1), Pb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃ (PLZT, 0<x<1, 0<y<1), (1-x) Pb(Mg_(1/3)Nb_(2/3))O₃-xPbTiO₃ (PMN-PT, 0<x<1), hafnia (HfO₂), SrTiO₃, SnO₂, CeO₂, MgO, NiO, CaO, ZnO, ZnO₂, ZrO₂, SiO₂, Y₂O₃, Al₂O₃, SiC, TiO₂, tetraethyl orthosilicate (TEOS), montmorillonite (MMT), (P₂O₅)₄ (ZrO₂)₃, P₂O₅—ZrO₂—SiO₂, CsDSO₄, CsHSO₄, α-Zn (O₃PCH₂OH)_(1.27) (O₃PC₆H₄SO₃H)_(0.73)nH₂O, γ-Zr (PO₄) (H₂PO₄)_(0.54) (HO₃PC₆H₄SO₃H)_(0.46)nH₂O, Zr(O₃PCH₂OH)_(1.27)Y_(0.73)nH₂O, α-Zr (O₃PC₆H₄SO₃H)_(3.6)H₂O, α-Zr(O₃POH)H₂O, β-Cs₃ (HSO₄)₂(Hx (P, S)O₄), αCs₃(HSO₄)₂(H₂PO₄), phosphotungstic acid, silicotungstic acid and molybdophosphoric acid (H₃PO₄12MoO₃zH₂O), however, the inorganic particles are not limited thereto.

In the present specification, n and z may have ranges of 1<n<10 and 1<z<10, respectively.

In one embodiment of the present specification, the inorganic particles are SiO₂.

In one embodiment of the present specification, the inorganic particles are provided in a dispersed form in the polymer electrolyte membrane.

In another embodiment, the content of the inorganic particles is from 0.05 weight % to 20 weight % and the content of the polymer is from 80 weight % to 99.95 weight % based on the total content of the polymer electrolyte membrane.

In one embodiment of the present specification, the content of the inorganic particles is from 0.05 weight % to 20 weight % based on the total solid content of the polymer electrolyte membrane. In another embodiment, the content of the inorganic particles is greater than or equal to 0.05 weight % and less than 10 weight % based on the total solid content of the polymer electrolyte membrane.

In the present specification, the solid means a solute or a solid excluding a solvent from the total mass of a solution.

In one embodiment of the present specification, the content of the polymer is preferably from 3 weight % to 30 weight % and more preferably from 5 weight % to 15 weight % based on the total content of the polymer electrolyte membrane.

In the present specification, the total content of the polymer electrolyte membrane may mean a content including all of the inorganic particles; the polymer including the unit of Chemical Formula 1; and a solvent.

When including the inorganic particles in the above-mentioned range, heat resistance and the degree of water retention at high temperatures of the polymer membrane may increase by the introduced inorganic particles, and decline in the mechanical properties may be prevented during high temperature swelling. In addition, in the above-mentioned range, the inorganic particles may contribute to an improvement in the hydrogen ion conductivity resulting from a decrease in the percentage of water content at high temperatures.

In one embodiment of the present specification, the polymer included in the polymer electrolyte membrane includes the unit represented by Chemical Formula 1.

In the present specification, an S atom is used as a linker of a —[CR1R2]_(n)-A structure and a benzene ring in Chemical Formula 1. In this case, an electron withdrawing character of the —[CR1R2]_(n)-A linked by the S atom allows the polymer to be readily formed, and a stable polymer may be provided.

In one embodiment of the present specification, R1 and R2 are the same as or different from each other, and each independently a halogen group. Specifically, R1 and R2 may be each independently selected from the group consisting of F; Cl; Br; and I.

When the polymer including the unit represented by Chemical Formula 1 of the present specification is included in the polymer electrolyte membrane and R1 and R2 of Chemical Formula 1 are a halogen group, there is an advantage in that electrons are favorably attracted increasing acidity of the A functional group at the end and thereby facilitating hydrogen ion migration, and the structure of the polymer electrolyte membrane is strengthened. Specifically, according to one embodiment of the present specification, the advantage may be maximized when R1 and R2 are fluorine.

In one embodiment of the present specification, n is an integer of 2 to 10. In another embodiment of the present specification, n is an integer of 2 to 6.

A monomer including the unit of Chemical Formula 1 according to one embodiment of the present specification may control the number of n. In this case, by controlling the length of the structure in the parenthesis, phase separation of the polymer electrolyte membrane may be readily accomplished, and hydrogen ion migration of the polymer electrolyte membrane may be facilitated.

In one embodiment of the present specification, n is 2.

In another embodiment, n is 3.

In another embodiment, n is 4.

In another embodiment, n is 5.

In another embodiment, n is 6.

In another embodiment, n is 7.

In one embodiment of the present specification, n is 8.

In another embodiment, n is 9.

In one embodiment of the present specification, n is 10.

In one embodiment of the present specification, A is —SO₃H or —SO₃ ⁻M⁺.

In another embodiment, A is —SO₃H.

As above, when A is —SO₃H or —SO₃ ⁻M⁺ in Chemical Formula 1, a chemically stable polymer may be formed.

In one embodiment of the present specification, M is a group 1 element.

The group 1 element in the present specification may be Li, Na or K.

In one embodiment of the present specification, the unit represented by Chemical Formula 1 is represented by any one of the following Chemical Formulae 1-1 to 1-9.

In one embodiment of the present specification, the polymer includes the unit represented by Chemical Formula 1 in 1 mol % to 100 mol %. Specifically, in one embodiment of the present specification, the polymer includes only the unit represented by Chemical Formula 1.

In another embodiment, the polymer may further include a different second unit in addition to the unit represented by Chemical Formula 1. In one embodiment of the present specification, when the polymer further includes a second unit, the content of the unit represented by Chemical Formula 1 is preferably from 5 mol % to 65 mol %.

The unit represented by Chemical Formula 1 according to one embodiment of the present specification performs a role of controlling ion conductivity of a separator.

The second unit according to another embodiment may be selected from among units enhancing mechanical strength of the polymer, and the type is not limited as long as it is a unit capable of enhancing mechanical strength.

In one embodiment of the present specification, the polymer included in the polymer electrolyte membrane is a random polymer. In this case, a polymer having a high molecular weight may be obtained using a simple polymerization method.

Specifically, in one embodiment of the present specification, the unit represented by Chemical Formula 1 and the second unit may form a random polymer.

According to one embodiment of the present specification, functional groups including a partial fluorine-based stretch out in a pendant form in the unit represented by Chemical Formula 1, and therefore, phase separation is readily obtained since partial fluorine-based functional groups in the polymer are favorably aggregated. Accordingly, ion channels are readily formed and ions are selectively exchanged enhancing ion conductivity of a separator.

In one embodiment of the present specification, the polymer included in the polymer electrolyte membrane is a block polymer including a hydrophilic block; and a hydrophobic block, and the hydrophilic block includes the unit represented by Chemical Formula 1.

In one embodiment of the present specification, the hydrophilic block and the hydrophobic block are included in a molar ratio of 1:0.1 to 1:10 in the block polymer. In one embodiment of the present specification, the hydrophilic block and the hydrophobic block are included in a molar ratio of 1:0.1 to 1:2 in the block polymer. In another embodiment, the hydrophilic block and the hydrophobic block are included in a molar ratio of 1:0.8 to 1:1.2 in the block polymer. In this case, an ion transfer ability of the block polymer may be enhanced.

In one embodiment of the present specification, the unit represented by Chemical Formula 1 is included in 0.01 mol % to 100 mol % in the hydrophilic block based on the hydrophilic block.

In one embodiment of the present specification, the hydrophilic block has a number average molecular weight of 1,000 g/mol to 300,000 g/mol. In a specific embodiment, the number average molecular weight is from 2,000 g/mol to 100,000 g/mol. In another embodiment, the number average molecular weight is from 2,500 g/mol to 50,000 g/mol.

In one embodiment of the present specification, the hydrophobic block has a number average molecular weight of 1,000 g/mol to 300,000 g/mol. In a specific embodiment, the number average molecular weight is from 2,000 g/mol to 100,000 g/mol. In another embodiment, the number average molecular weight is from 2,500 g/mol to 50,000 g/mol.

According to an embodiment of the present specification, the hydrophilic block and the hydrophobic block are clearly divided and separated in the block polymer and phase separation is readily obtained, and therefore, ions are readily transferred. According to one embodiment of the present specification, the hydrophilic block and the hydrophobic block are more clearly divided when including the unit represented by Chemical Formula 1, and an ion transfer effect may be more superior than existing polymers.

In the present specification, the “block polymer” means a polymer formed by one block, and one, two or more blocks that are different from the one block being linked to each other by a polymer main chain.

The “hydrophilic block” of the present specification means a block having an ion-exchange group as a functional group. Herein, the functional group may mean A in Chemical Formula 1 described above. That is, the ion-exchange group may be one or two types selected from the group consisting of —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁻, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻2M⁺, —O(CF₂)_(n)SO₃H, —O(CF₂)_(n)SO₃ ⁻M⁺, —O(CF₂)_(n)COOH, —O(CF₂)_(n)COO⁻M⁺, —O(CF₂)_(n)PO₃H₂, —O(CF₂)_(n)PO₃H⁻M⁺ and —O(CF₂)_(n)PO₃ ²⁻2M⁺. Herein, M may be a metallic element. In other words, the functional group may be hydrophilic.

The “block having an ion-exchange group” of the present specification means a block including an average of 0.5 or more ion-exchange groups when representing as the number of ion-exchange groups per one structure unit forming the corresponding block, and including an average of 1.0 or more ion-exchange groups per one structure unit is more preferred.

The “hydrophobic block” of the present specification means the polymer block that does not substantially include an ion-exchange group.

The “block that does not substantially include an ion-exchange group” of the present specification means a block including an average of less than 0.1 ion-exchange groups when representing as the number of ion-exchange groups per one structure unit forming the corresponding block, and including an average of 0.05 or less is more preferred, and a block that does not include an ion-exchange group at all is even more preferred.

In one embodiment of the present specification, the polymer further includes a brancher derived from a compound represented by the following Chemical Formula 2; or a brancher represented by the following Chemical Formula 3.

In Chemical Formulae 2 and 3,

X is S; O; CO; SO; SO₂; NR; a hydrocarbon-based or fluorine-based assembly,

l is an integer of 0 to 10,

when 1 is 2 or greater, two or more Xs are the same as or different from each other,

Y1 and Y2 are the same as or different from each other, and each independently NRR; an aromatic ring in which one, two or more are substituted with substituents selected from the group consisting of a hydroxyl group and a halogen group; or an aliphatic ring in which one, two or more are substituted with substituents selected from the group consisting of a hydroxyl group and a halogen group,

R is an aromatic ring substituted with a halogen group; or an aliphatic ring substituted with a halogen group, and

Z is a trivalent organic group.

In the present specification, the “brancher” performs a role of linking or crosslinking polymer chains.

In the present specification, the “derived” means producing new bonds as bonds of a compound are cut or substituents fall off, and the unit derived from the compound may mean a unit linked to a main chain of a polymer. The unit may form a polymer by being included in a main chain of the polymer.

In the polymer further including the brancher in the present specification, the brancher may directly form a main chain of the polymer, and a mechanical degree of integration of a thin membrane may be enhanced.

Specifically, in the branched polymer of the present disclosure, the brancher directly forms a main chain of the polymer without carrying out a post-sulfonation reaction or a cross-linking reaction of a sulfonated polymer by polymerizing branched hydrophobic blocks that do not include acid substituents and branched hydrophilic blocks that include acid substituents, and the hydrophobic blocks maintaining a mechanical degree of integration of a thin membrane and the hydrophilic blocks providing ion conductivity to the thin membrane are alternately linked through chemical bonds.

Examples of the substituents of the present specification are described below, however, the substituents are not limited thereto.

In the present specification,

means binding to adjacent substituents or a main chain of a polymer.

Specifically, the brancher derived from the compound of Chemical Formula 2 in the present specification may function as a brancher as, in each of Y1 and Y2, an aromatic ring substituted with a hydroxyl group and/or a halogen group; or an aliphatic ring substituted with a hydroxyl group and/or a halogen group, the hydroxyl group and/or the halogen group fall off from the aromatic ring or the aliphatic ring. Specifically, the brancher derived from the compound of Chemical Formula 2 in the present specification may function as a brancher in the polymer as two or more hydroxyl groups and/or halogen groups fall off.

The term “substitution” means a hydrogen atom bonding to a carbon atom of a compound is changed to another substituent, and the position of substitution is not limited as long as it is a position at which the hydrogen atom is substituted, that is, a position at which a substituent can substitute, and when two or more substituents substitute, the two or more substituents may be the same as or different from each other.

In the present specification, the hydrocarbon-based means an organic compound formed only with carbon and hydrogen, and includes linear, branched, cyclic hydrocarbon and the like, and is not limited. In addition, a single bond, a double bond or a triple bond may be included, and the hydrocarbon-based is not limited.

In the present specification, a fluorine-based assembly means a part or all of carbon-hydrogen bonds in the hydrocarbon-based are substituted with fluorine.

In the present specification, the aromatic ring may be an aromatic hydrocarbon ring or an aromatic heteroring, and may be monocyclic or multicyclic.

Specifically, examples of the aromatic hydrocarbon ring may include a monocyclic aromatic group such as a phenyl group, a biphenyl group and a terphenyl group, and a multicyclic aromatic group such as a naphthyl group, a binaphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, a perylenyl group, a tetracenyl group, a chrysenyl group, a fluorenyl group, an acenaphthacenyl group, a triphenylene group and a fluoranthene group, but are not limited thereto.

In the present specification, the aromatic heteroring means a structure including one or more heteroatoms such as O, S, N and Se instead of a carbon atom in the aromatic hydrocarbon ring. Specific examples thereof may include a thiophene group, a furan group, a pyrrole group, an imidazole group, a thiazole group, an oxazole group, an oxadiazole group, a triazole group, a pyridyl group, a bipyridyl group, a pyrimidyl group, a triazine group, a triazole group, an acridyl group, a pyridazine group, a pyrazinyl group, a quinolinyl group, a quinazoline group, a quinoxalinyl group, a phthalazinyl group, a pyridopyrimidinyl group, a pyridopyrazinyl group, a pyrazinopyrazinyl group, an isoquinoline group, an indole group, a carbazole group, a benzoxazole group, a benzimidazole group, a benzothiazole group, a benzocarbazole group, a benzothiophene group, a dibenzothiophene group, a benzofuranyl group, a phenanthroline group, a thiazolyl group, an isoxazolyl group, an oxadiazolyl group, a thiadiazolyl group, a benzothiazolyl group, a phenothiazinyl group, a dibenzofuranyl group and the like, but are not limited thereto.

In the present specification, the aliphatic ring may be an aliphatic hydrocarbon ring or an aliphatic heteroring, and may be monocyclic or multicyclic. Examples of the aliphatic ring may include a cyclopentyl group, a cyclohexyl group and the like, but are not limited thereto.

In the present specification, the organic group may include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group and the like. This organic group may include bonds or substituents besides a hydrocarbon group such as heteroatoms in the organic group. In addition, the organic group may be any of linear, branched or cyclic.

In the present specification, the trivalent organic group means a trivalent group having 3 binding sites in an organic compound.

In addition, the organic group may form a cyclic structure, and may form bonds including heteroatoms as long as it does not harm effects of the present disclosure.

Specifically, bonds including heteroatoms such as an oxygen atom, a nitrogen atom and a silicon atom may be included. Specific examples thereof may include ether bonds, thioether bonds, carbonyl bonds, thiocarbonyl bonds, ester bonds, amide bonds, urethane bonds, imino bonds (—N═C(-A)-, —C(═NA)—: A represents a hydrogen atom or an organic group), carbonate bonds, sulfonyl bonds, sulfinyl bonds, azo bonds and the like, but are not limited thereto.

Examples of the cyclic structure may include the aromatic ring, the aliphatic ring and the like described above, and the cyclic structure may be monocyclic or multicyclic.

In the present specification, the alkyl group may be linear or branched, and although not particularly limited thereto, the number of carbon atoms is preferably from 1 to 50. Specific examples thereof may include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group and the like, but are not limited thereto.

In the present specification, the alkenyl group may be linear or branched, and although not particularly limited thereto, the number of carbon atoms is preferably from 2 to 40. Specific examples thereof may include vinyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 3-methyl-1-butenyl, 1,3-butadienyl, allyl, 1-phenylvinyl-1-yl, 2-phenylvinyl-1-yl, 2,2-diphenylvinyl-1-yl, 2-phenyl-2-(naphthyl-1-yl)vinyl-1-yl, 2,2-bis(diphenyl-1-yl)vinyl-1-yl, a stilbenyl group, a styrenyl group and the like, but are not limited thereto.

In the present specification, the cycloalkyl group is not particularly limited, but preferably has 3 to 60 carbon atoms, and particularly, may include a cyclopentyl group, a cyclohexyl group and the like, but is not limited thereto.

In one embodiment of the present specification, 1 is 3 or greater.

In one embodiment of the present specification, X is S.

In another embodiment, X is a haloalkyl group.

In another embodiment, X is CH₂.

In another embodiment of the present specification, X is NR.

In one embodiment of the present specification, Y1 and Y2 are the same as or different from each other, and each independently a halogen-substituted aromatic ring.

In one embodiment of the present specification, Y1 and Y2 are the same as or different from each other, and each independently a fluorine-substituted aromatic hydrocarbon ring.

In one embodiment of the present specification, Y1 and Y2 are the same as or different from each other, and each independently NRR.

In another embodiment, Y1 and Y2 are each a fluorine-substituted phenyl group. Specifically, 2,4-phenyl, 2,6-phenyl, 2,3-phenyl, 3,4-phenyl and the like are included, however, Y1 and Y2 are not limited thereto.

In one embodiment of the present specification, the compound represented by Chemical Formula 2 may be represented by any one of the following structures.

In the structures, definitions of X, 1 and R are the same as in Chemical Formula 2.

According to one embodiment of the present specification, Z in Chemical Formula 3 may be represented by any one of the following Chemical Formulae 3-1 to 3-4.

In Chemical Formulae 3-1 to 3-4,

L1 to L7 are the same as or different from each other, and each independently a direct bond; —S—; —O—; —CO—; or —SO₂—,

R10 to R20 are the same as or different from each other, and each independently hydrogen; deuterium; a halogen group; a cyano group; a nitrile group; a nitro group; a hydroxyl group; a substituted or unsubstituted alkyl group; a substituted or unsubstituted cycloalkyl group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted alkenyl group; a substituted or unsubstituted aryl group; or a substituted or unsubstituted heteroaryl group,

a, b, c, f, h, i and j are each an integer of 1 to 4,

d, e and g are each an integer of 1 to 3,

k is an integer of 1 to 6, and

when a, b, c, d, e, f, g, h, i, j and k are each an integer of 2 or greater, structures in the two or more parentheses are the same as or different from each other.

In one embodiment of the present specification, L1 is CO.

In another embodiment, L1 is SO₂.

In another embodiment, L1 is S.

In another embodiment, L2 is CO.

In another embodiment, L2 is SO₂.

In another embodiment, L2 is S.

In one embodiment of the present specification, L3 is CO.

In another embodiment, L3 is SO₂.

In another embodiment, L3 is S.

In one embodiment of the present specification, L4 is CO.

In another embodiment, L4 is SO₂.

In one embodiment of the present specification, R10 to

R20 are hydrogen.

In one embodiment of the present specification, R16 is a halogen group.

In another embodiment, R16 is fluorine.

In addition, in one embodiment of the present specification, the brancher represented by Chemical Formula 3 may be represented by any one of the following structures.

In one embodiment of the present specification, the polymer has a weight average molecular weight of 500 g/mol to 5,000,000 g/mol. In another embodiment of the present specification, the polymer has a weight average molecular weight of 10,000 g/mol to 3,000,000 g/mol. When the polymer has a weight average molecular weight in the above-mentioned range, mechanical properties of the electrolyte membrane including the polymer do not decline, and proper polymer solubility is maintained, and therefore, the electrolyte membrane may be readily prepared.

The polymer electrolyte membrane according to one embodiment of the present specification may be prepared using materials and/or methods known in the art except for including the polymer including the unit represented by Chemical Formula 1 and inorganic particles. For example, a method of coating a solution including the polymer, and then drying and/or curing the result may be carried out.

In one embodiment of the present specification, the coating may use methods such as a tape casting method, a dip coating method, a spray coating method and a spin coating method.

In one embodiment of the present specification, N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N,N-dimethylpyrrolidone (NMP), diphenyl sulfone, N,N-dimethylformamide (DMF) and the like may be used as the solvent used in the preparation of the polymer electrolyte membrane, however, the solvent is not limited thereto.

The curing may be carried out by heating.

In one embodiment of the present specification, the heating means curing through heating.

In one embodiment of the present specification, the heating temperature may be higher than or equal to 30° C. and lower than or equal to 200° C., and specifically higher than or equal to 50° C. and lower than or equal to 150° C. In one embodiment of the present specification, the heating time may be longer than or equal to 1 hour and shorter than or equal to 46 hours, and specifically longer than or equal to 5 hours and shorter than or equal to 20 hours.

In one embodiment of the present specification, the method for preparing the electrolyte membrane may further include adding an acid solution to the solution including the polymer.

In one embodiment of the present specification, when an acid solution is added to the solution including the polymer, the metal M of a copolymer in which A of Chemical Formula 1 is —SO³, —M⁺, —COO⁻M⁺, —PO₃H⁻M⁺ or —PO₃ ²⁻2M⁺ may be substituted with hydrogen (H).

In one embodiment of the present specification, the heating may be preheating for 2 hours to 6 hours at 50° C. to 70° C., drying for 12 hours or longer at 100° C., and lastly drying for 12 hours or longer in a 100° C. vacuum oven.

According to one embodiment of the present specification, the polymer electrolyte membrane has ion conductivity of 0.01 S/cm to 0.5 S/cm. In another embodiment, the polymer electrolyte membrane has ion conductivity of greater than or equal to 0.01 S/cm and less than or equal to 0.3 S/cm.

In one embodiment of the present specification, ion conductivity of the polymer electrolyte membrane may be measured under a humidity condition. A humidity condition in the present specification may mean relative humidity (RH) of 10% to 100%.

In addition, in one embodiment of the present specification, the polymer electrolyte membrane has an ion exchange capacity (IEC) value of 0.01 mmol/g to 5 mmol/g. When the polymer electrolyte membrane has an ion exchange capacity value in the above-mentioned range, ion channels are formed in the polymer electrolyte membrane, and the polymer may exhibit ion conductivity.

In one embodiment of the present specification, the polymer electrolyte membrane has a thickness of 1 μm to 500 μm. The polymer electrolyte membrane having the above-mentioned thickness range reduces electric short and electrolyte material crossover, and may exhibit an excellent cation conductivity property.

In one embodiment of the present specification, the polymer electrolyte membrane is a pure membrane including only a polymer including the unit represented by Chemical Formula 1; and inorganic particles.

In another embodiment, the polymer electrolyte membrane is a reinforced membrane further including a substrate.

In other words, one embodiment of the present specification provides a reinforced membrane including a substrate; a polymer including the unit represented by Chemical Formula 1; and inorganic particles.

In one embodiment of the present specification, the ‘reinforced membrane’ is an electrolyte membrane including a substrate, a reinforcing material, and a membrane capable of exchanging ions, and may mean a substrate-including membrane, ion-exchange membrane, ion-transfer membrane, ion-conductive membrane, separator, ion-exchange separator, ion-transfer separator, ion-conductive separator, ion-exchange electrolyte membrane, ion-transfer electrolyte membrane, ion-conductive electrolyte membrane or the like.

In the present specification, the substrate may mean a support having a three-dimensional network structure, and the reinforced membrane including the substrate and the polymer may mean the polymer being included in at least a part of one surface of the substrate, a surface opposite to the one surface and a pore region inside the substrate. In other words, the reinforced membrane of the present specification may be provided in a form of the polymer being impregnated in the substrate.

The polymer and the inorganic particles are the same as described above.

Hydrocarbon-based ion-transfer separators have problems in that an ion transfer ability is inferior compared to fluorine-based separators, and chemical resistance is weak. Accordingly, by including the polymer including the unit represented by Chemical Formula 1, the reinforced membrane according to one embodiment of the present specification has high mechanical strength and high ion conductivity, and phase separation of the reinforced membrane may be readily accomplished.

In addition, by including the substrate, the reinforced membrane according to one embodiment of the present specification enhances chemical resistance and durability, and thereby enhances a lifespan of a device.

In one embodiment of the present specification, one or two types from the group consisting of polypropylene (PP), polytetrafluoroethylene (PTFE), polyethylene (PE) and polyvinylidene fluoride (PVDF) are selected as the substrate.

In one embodiment of the present specification, the content of the polymer and the inorganic particles is from 10 parts by weight to 99 parts by weight with respect to 100 parts by weight of the reinforced membrane.

In another embodiment, the content of the polymer and the inorganic particles is from 10 parts by weight to 99 parts by weight and the content of the substrate is from 1 part by weight to 90 parts by weight, with respect to 100 parts by weight of the reinforced membrane. As the content of the substrate increases, a vanadium ion crossover may be reduced, and as the content of the polymer increases, battery performance may be enhanced.

Accordingly, when the content of the substrate, the polymer and the inorganic particles according to one embodiment of the present specification is in the above-mentioned range, a vanadium ion crossover may be reduced while maintaining battery performance.

According to one embodiment of the present specification, the reinforced membrane has ion conductivity of greater than or equal to 0.001 S/cm and less than or equal to 0.5 S/cm. In another embodiment, the reinforced membrane has ion conductivity of greater than or equal to 0.001 S/cm and less than or equal to 0.3 S/cm.

In the present specification, ion conductivity may be measured under the same condition as described above.

In addition, in one embodiment of the present specification, the reinforced membrane has an ion exchange capacity (IEC) value of 0.01 mmol/g to 5.0 mmol/g. When the reinforced membrane has an ion exchange capacity value in the above-mentioned range, ion channels are formed in the reinforced membrane, and the polymer may exhibit ion conductivity.

In one embodiment of the present specification, the reinforced membrane has a thickness of 0.01 μm to 10,000 μm. The reinforced membrane having the above-mentioned thickness range reduces electric short and electrolyte material crossover, and may exhibit an excellent cation conductivity property.

One embodiment of the present specification also provides a method for preparing a reinforced membrane including preparing a substrate; and impregnating the substrate into a mixed solution of the polymer and the inorganic particles.

In the present specification, impregnation means a polymer and inorganic particles infiltrating into a substrate. The impregnation in the present specification may be carried out by dipping the substrate into the mixed solution of the polymer and the inorganic particles, slot die coating, bar casting and the like.

In the present specification, dipping may be expressed by terms such as dip coating or dipping method.

In one embodiment of the present specification, the reinforced membrane may have directivity. Specifically, in one embodiment of the present specification, the substrate may be prepared through monoaxial orientation or biaxial orientation, and directivity of the substrate obtained by the orientation may determine directivity of the reinforced membrane. Therefore, the reinforced membrane according to one embodiment of the present specification may have directivity in a machine direction (MD) and in a direction perpendicular to the machine direction (MD), and the reinforced membrane may exhibit differences in the properties such as stress and elongation depending on the directivity.

One embodiment of the present specification also provides a method for preparing a reinforced membrane including preparing a substrate; and dipping the substrate into a mixed solution of the polymer including the unit represented by Chemical Formula 1 and the inorganic particles.

In the present specification, the substrate, the polymer and the inorganic particles are the same as described above.

One embodiment of the present specification also provides a membrane-electrode assembly including an anode; a cathode; and the polymer electrolyte membrane described above provided between the anode and the cathode.

The membrane-electrode assembly (MEA) means an assembly of electrodes (cathode and anode) in which an electrochemical catalyst reaction of fuel and air occurs and a polymer membrane in which hydrogen ion transfer occurs, and is a single assembled unit in which electrodes (cathode and anode) and an electrolyte membrane are adhered.

The membrane-electrode assembly of the present specification has a form of a catalyst layer of an anode and a catalyst layer of a cathode being brought into contact with an electrolyte membrane, and may be prepared using common methods known in the art. As one example, the membrane-electrode assembly may be prepared through thermocompressing the cathode; the anode; and the electrolyte membrane located between the cathode and the anode at 100° C. to 400° C. while sticking these together.

The anode electrode may include an anode catalyst layer and an anode gas diffusion layer. The anode gas diffusion layer may again include an anode micropore layer and an anode electrode substrate.

The cathode electrode may include a cathode catalyst layer and a cathode gas diffusion layer. The cathode gas diffusion layer may again include a cathode micropore layer and a cathode electrode substrate.

FIG. 1 is a diagram schematically showing a principle of electricity generation of a fuel cell, and in the fuel cell, a most basic unit generating electricity is a membrane-electrode assembly (MEA), and this is formed with an electrolyte membrane (100), and anode (200 a) and cathode (200 b) electrodes formed on both sides of the electrolyte membrane (100). When referring to FIG. 1 showing a principle of electricity generation of a fuel cell, an oxidation reaction of fuel such as hydrogen, methanol, or hydrocarbon such as butane occurs in the anode (200 a) to generate hydrogen ions (H⁻) and electrons (e⁻), and the hydrogen ions migrate to the cathode (200 b) through the electrolyte membrane (100). In the cathode (200 b), water is produced through the reaction of the hydrogen ions transferred through the electrolyte membrane (100), an oxidizer such as oxygen, and electrons. Electrons migrate to an external circuit through such a reaction.

The anode electrode catalyst layer is a place where an oxidation reaction of fuel occurs, and catalysts selected from the group consisting of platinum, ruthenium, osmium, platinum-ruthenium alloys, platinum-osmium alloys, platinum-palladium alloys and platinum-transition metal alloys may be preferably used. The cathode electrode catalyst layer is a place where a reduction reaction of an oxidizer occurs, and platinum or platinum-transition metal alloys may be preferably used as catalysts. The catalysts may be used as they are, or may be used while being supported on a carbon-based carrier.

The process of introducing the catalyst layer may be carried out using common methods known in the art, and for example, a catalyst ink may be directly coated on the electrolyte membrane, or coated on the gas diffusion layer to form the catalyst layer. Herein, the coating method of the catalyst ink is not particularly limited, and methods of spray coating, tape casting, screen printing, blade coating, die coating, spin coating or the like may be used. The catalyst ink may be typically formed with a catalyst, a polymer ionomer and a solvent.

The gas diffusion layer becomes a migration path of reaction gases and water while performing a role of a current conductor, and has a porous structure. Accordingly, the gas diffusion layer may be formed including a conductive substrate. As the conductive substrate, carbon paper, carbon cloth or carbon felt may be preferably used. The gas diffusion layer may be formed further including a micropore layer between the catalyst layer and the conductive substrate. The micropore layer may be used for enhancing fuel cell performance under a low humidity condition, and performs a role of allowing the electrolyte membrane to be under a sufficiently wet condition by having the amount of water escaping outside the gas diffusion layer being small.

One embodiment of the present specification provides a polymer electrolyte-type fuel cell including two or more membrane-electrode assemblies; a stack including a bipolar plate provided between the membrane-electrode assemblies; a fuel supplying unit supplying fuel to the stack; and an oxidizer supplying unit supplying an oxidizer to the stack.

A fuel cell is an energy conversion device directly converting chemical energy of fuel into electric energy. In other words, a fuel cell employs a power generation method utilizing a fuel gas and an oxidizer, and using electrons generated during the oxidation and reduction reactions thereof to produce power.

The fuel cell may be prepared through common methods known in the art using the membrane-electrode assembly (MEA) described above. For example, the fuel cell may be prepared by forming with the membrane-electrode assembly (MEA) prepared above and a bipolar plate.

The fuel cell of the present specification is formed including a stack, a fuel supplying unit and an oxidizer supplying unit.

FIG. 3 is a diagram schematically illustrating the fuel cell, and the fuel cell is formed including a stack (60), an oxidizer supplying unit (70) and a fuel supplying unit (80).

The stack (60) includes one, two or more of the membrane-electrode assemblies described above, and when two or more of the membrane-electrode assemblies are included, a separator provided therebetween is included. The separator prevents the membrane-electrode assemblies from being electrically connected, and performs a role of transferring fuel and oxidizer supplied from the outside to the membrane-electrode assemblies.

The oxidizer supplying unit (70) performs a role of supplying an oxidizer to the stack (60). As the oxidizer, oxygen is typically used, and oxygen or air may be injected with a pump (70) to be used.

The fuel supplying unit (80) performs a role supplying fuel to the stack (60), and may be formed with a fuel tank (81) storing fuel, and a pump (82) supplying the fuel stored in the fuel tank (81) to the stack (60). As the fuel, hydrogen or hydrocarbon fuel in a gas or liquid state may be used. Examples of the hydrocarbon fuel may include methanol, ethanol, propanol, butanol or natural gas.

The fuel cell may include a polymer electrolyte fuel cell, a direct liquid fuel cell, a direct methanol fuel cell, a direct formic acid fuel cell, a direct ethanol fuel cell, a direct dimethyl ether fuel cell or the like.

When using the electrolyte membrane according to one embodiment of the present specification as an ion-exchange membrane of the fuel cell, effects described above may be obtained.

In addition, one embodiment of the present specification provides a redox flow battery including a positive electrode cell including a positive electrode and a positive electrode liquid electrolyte; a negative electrode cell including a negative electrode and a negative electrode liquid electrolyte; and the polymer electrolyte membrane according to one embodiment of the present specification provided between the positive electrode cell and the negative electrode cell.

A redox flow battery (oxidation-reduction flow battery) is a system charged and discharged by active materials included in a liquid electrolyte being oxidized and reduced, and is an electrochemical storage device directly storing chemical energy of the active materials as electric energy. A redox flow battery uses a principle of being charged and discharged from the exchange of electrons occurring when liquid electrolytes including active materials in different oxidation states meet with an ion-exchange membrane in between. A redox flow battery is generally formed with a tank holding a liquid electrolyte, a battery cell where charge and discharge occur, and a circulating pump for circulating the liquid electrolyte between the tank and the battery cell, and a unit cell of the battery cell includes an electrode, an electrolyte and an ion-exchange membrane.

When using the electrolyte membrane according to one embodiment of the present specification as an ion-exchange membrane of the redox flow battery, effects described above may be obtained.

The redox flow battery of the present specification may be prepared using common methods known in the art except that the redox flow battery includes the polymer electrolyte membrane according to one embodiment of the present specification.

As illustrated in FIG. 2, the redox flow battery is divided into a positive electrode cell (32) and a negative electrode cell (33) by an electrolyte membrane (31). The positive electrode cell (32) and the negative electrode cell (33) include a positive electrode and a negative electrode, respectively. The positive electrode cell (32) is connected to a positive electrode tank (10) for supplying and releasing a positive electrode liquid electrolyte (41) through a pipe. The negative electrode cell (33) is also connected to a negative electrode tank (20) for supplying and releasing a negative electrode liquid electrolyte (42) through a pipe. The liquid electrolytes circulate through pumps (11, 21), and through an oxidation/reduction reaction (that is, a redox reaction) changing the oxidation number of ions, charge and discharge occur in the positive electrode and the negative electrode.

Hereinafter, the present specification will be described in detail with reference to examples. However, the examples according to the present specification may be modified to various other forms, and the scope of the present specification is not to be construed as being limited to the examples described below. Examples of the present specification are provided in order to more completely describe the present specification to those having average knowledge in the art.

PREPARATION EXAMPLE 1

A polymer was prepared by mixing each monomer and potassium carbonate (K₂CO₃: molar ratio 4) in a 20 wt % ratio of NMP and a 20 wt % ratio of benzene, and polymerizing the result for 4 hours at 140° C. and 16 hours at 180° C. A molecular weight of the polymer was measured and is shown in the following Table 1.

COMPARATIVE EXAMPLE 1

As a result of carrying out a test obtaining a polymer with a 2,4-difluoro partial fluorine-based monomer, a unit represented by Chemical Formula 1 in Example 1, a high molecular weight polymer was successfully obtained. However, when attempting to prepare a polymer using a generally used 2,5-difluoro partial fluorine-based monomer, obtaining a high molecular weight polymer was unsuccessful under the same condition. The molecular weight of the polymer was measured through gel permeation chromatography (GPC) and is shown in the following Table 1.

COMPARATIVE EXAMPLE 2

A polymer was attempted to be prepared in the same manner as in Comparative Example 1 using a monomer of SO₂ instead of an S atom as a linker of a —[CR1R2]_(n)-A structure and a benzene ring in Chemical Formula 1, however, obtaining a high molecular weight polymer was unsuccessful under the same condition. The molecular weight of the polymer was measured through gel permeation chromatography (GPC) and is shown in the following Table 1.

TABLE 1 Partial Fluorine-based Membrane Mn (g/mol) Mw (g/mol) Mw/Mn Preparation Example 1 84,000 622,000 7.40 Comparative Example 1 N/A N/A N/A Comparative Example 2 N/A N/A N/A

In Table 1, N/A means not available, and it was identified that the polymer was not formed.

Based on the results of Preparation Example 1 and Comparative Example 2, a monomer substituted with functional groups at 2,5 positions, which has been generally used in the art, has been commercially used without considering reactivity even when reactivity is very different during a polymerization reaction depending on the properties of functional group substituting other positions.

It can be identified that, by the functional group of Chemical Formula 2 hung as a pendant generally having an electron withdrawing characteristic, the 2,4-difluoro halogenated compound according to one embodiment of the present specification exhibits greatly enhanced reactivity during a polymerization reaction, which is advantageous in obtaining a high molecular weight polymer.

Based on the results of Preparation Example 1 and Comparative Example 3, the compound including the unit represented by Chemical Formula 1 according to one embodiment of the present specification is chemically stable, and readily forms a polymer.

In the following examples and the comparative example, a separator was prepared using the polymer obtained in Preparation Example 1, a molecular weight of the separator was measured through GPC, and results of measuring cation conductivity and ion exchange capacity (IEC) of the pure membrane were described.

EXAMPLE 1

To an ion transfer resin solution (viscosity 500 cP, IEC 2.3) including a polymer in the manner of Preparation Example 1, a silica nanoparticle (size: ˜10 nm) solution was introduced in a 0.5 wt % ratio (solvent NMP), and the result was stirred for 4 hours at room temperature.

After the result was coated on a glass substrate and dried, a film having a size of approximately 40 μm was prepared.

EXAMPLE 2

A film was prepared in the same manner as in Example 1 except that the silica nanoparticle solution was included in a 2 wt % ratio.

EXAMPLE 3

A film was prepared in the same manner as in Example 1 except that the silica nanoparticle solution was included in a 10 wt % ratio.

COMPARATIVE EXAMPLE 3

A film was prepared in the same manner as in Example 1 except that silica nanoparticles were included.

Properties of the films prepared in Examples 1 to 3 and Comparative Example 3 were measured using the following methods, and the results are shown in Table 2.

IEC means ion exchange capacity, and was measured using a method of precipitating the film in a saturated aqueous sodium chloride (NaCl) solution for 24 hours, and calculating the amount of released hydrogen ions (H⁺) through sodium hydroxide titration.

In addition, water uptake was calculated through, after dipping the film in ultrapure water for 24 hours, a weight difference before and after the dipping. The percentage of water content may be defined by the following Equation 1. Weight of Film before Dipping/(Weight of Film after Dipping-Weight of Film before Dipping)×100  [Equation 1]

A swelling ratio was calculated by the following Equation 2 after dipping the dried film in distilled water for 24 hours at room temperature and then measuring the film thicknesses before and after the dipping. Swollen Length of Film after Dipping/Length of Film before Dipping×100  [Equation 2]

As for ion conductivity of the film, dependence on humidity was measured using an alternating current impedance method with a four-electrode cell in which temperature and humidity are controlled. After maintaining the cell for 2 hours or longer in a humid section and fully reaching an equilibrium state, ion conductivity was measured.

Ion conductivity 1 was measured using the method described above under a condition of relative humidity (RH) of 100% and 25° C., and ion conductivity 2 was measured using the method described above under a condition of relative humidity of 50% and 60° C.

As for vanadium ion transmittance, the prepared film was placed in a redox flow battery cell and clamped, and while circulating a solution dissolving 1 M magnesium sulfate (MgSO₄) in 2 M sulfuric acid (H₂SO₄) in a negative electrode and a solution dissolving 1 M vanadium oxysulfate (VOSO₄) in 2 M sulfuric acid (H₂SO₄) in a positive electrode, a vanadium ion concentration in the negative electrode was measured by the time, and the transmittance was calculated using the following Equation 3.

The vanadium ion concentration was converted by measuring absorbance at a tetravalent ion wavelength of 767 nm using a UV spectrophotometer (Shimadzu UV-1650PC).

$\begin{matrix} {{V\frac{dCt}{dt}} = {A\frac{P}{L}\left( {C_{0} - C_{t}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$

In Equation 3,

V means a volume of a sulfuric acid solution,

C₀ means an initial vanadium ion concentration in a magnesium sulfate tank,

C_(t) means a vanadium concentration in a magnesium sulfate tank at the time of t,

A means an area of the film in contact with a sulfuric acid solution,

P means vanadium ion transmittance, and

L means a film thickness.

TABLE 2 Water Swelling Ion Ion Vanadium Ion IEC Uptake Ratio Conductivity 1 Conductivity 2 Transmittance (meq/g) (%) (%) (S/cm) (S/cm) (10⁻⁵ cm²/min) Example 1 2.2 190 120 0.12 0.04 10.3 Example 2 2.1 76 72 0.1 0.08 3.6 Example 3 1.3 21 23 0.05 0.04 0.1 Comparative 2.3 200 150 0.12 0.03 12.3 Example 3

Based on the results of Table 2, the comparative example that did not include inorganic particles had excellent ion conductivity in terms of application in a fuel cell or a redox flow battery, but had high water uptake, swelling ratio and vanadium ion transmittance, which may be disadvantageous in the application in a membrane-electrode assembly or a redox flow battery.

According to one embodiment of the present specification, it was identified that the polymer electrolyte membrane further including inorganic particles in addition to the polymer had an excellent water-containing ability while maintaining ion conductivity to be used in a fuel cell or a redox flow battery, and had excellent ion conductivity under a low humidity condition.

Based on the above-described results, it was identified that heat resistance and the degree of water retention at high temperatures of the polymer membrane increased by the introduced inorganic particles. However, when the content of the inorganic particles was 10 weight % or greater, ion conductivity decreased, and based on this result, it was identified that a problem of even dispersion may act as a main factor in the performance.

In addition, it was identified that the polymer electrolyte membrane according to one embodiment of the present specification had excellent water uptake, swelling ratio and vanadium ion transmittance compared to when inorganic particles were not included.

FIG. 4 is an image measuring a surface of the film according to Example 2 using a scanning electron microscope (SEM). 

The invention claimed is:
 1. A polymer electrolyte membrane comprising: a polymer including a unit represented by the following Chemical Formula 1; and inorganic particles:

wherein, in Chemical Formula 1, A is —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻2M⁺, —O(CF₂)_(m)SO₃H, —O(CF₂)_(m)SO₃ ⁻M⁺, −O(CF₂)_(m)COOH, −O(CF₂)_(m)COO⁻M⁺, —O(CF₂)_(m)PO₃H₂, —O(CF₂)_(m)PO₃H⁻M⁺or —O(CF₂)_(m)PO₃ ²⁻2M⁺; m is an integer of 2 to 6; M is a group 1 element; R1 and R2 are the same as or different from each other, and each independently a halogen group; and n is an integer of 2 to 10, and structures in the 2 to 10 parentheses are the same as or different from each other.
 2. The polymer electrolyte membrane of claim 1, wherein the inorganic particles have a particle diameter of 5 nm to 50 μm.
 3. The polymer electrolyte membrane of claim 1, wherein the inorganic particles are one, two or more selected from the group consisting of inorganic matters, heteropolyacids and inorganic acids.
 4. The polymer electrolyte membrane of claim 1, wherein the inorganic particles are provided in a dispersed form in the polymer electrolyte membrane.
 5. The polymer electrolyte membrane of claim 1, wherein, based on a total solid content of the polymer electrolyte membrane, a content of the inorganic particles is from 0.05 weight % to 20 weight %, and a content of the polymer is from 80 weight % to 99.95weight %.
 6. The polymer electrolyte membrane of claim 1, wherein a first unit represented by Chemical Formula 1 is represented by any one of the following Chemical Formulae 1-1 to 1-9:


7. The polymer electrolyte membrane of claim 1, wherein the polymer includes the unit represented by Chemical Formula 1 in 1 mol % to 100 mol %.
 8. The polymer electrolyte membrane of claim 1, wherein the polymer is a random polymer.
 9. The polymer electrolyte membrane of claim 1, wherein the polymer is a block polymer including a hydrophilic block; and a hydrophobic block, and the hydrophilic block includes the unit represented by Chemical Formula
 1. 10. The polymer electrolyte membrane of claim 9, wherein the hydrophilic block and the hydrophobic block are included in a molar ratio of 1:0.1 to 1:10 in the polymer.
 11. The polymer electrolyte membrane of claim 1, wherein the polymer further includes a brancher derived from a compound represented by the following Chemical Formula 2; or a brancher represented by the following Chemical Formula 3:

wherein, in Chemical Formulae 2 and 3, X is S; O; CO; SO; SO_(2;) NR; a hydrocarbon-based or fluorine-based assembly; 1 is an integer of 0 to 10; when 1 is 2 or greater, two or more Xs are the same as or different from each other; Y1 and Y2 are the same as or different from each other, and each independently NRR; an aromatic ring in which one, two or more are substituted with substituents selected from the group consisting of a hydroxyl group and a halogen group; or an aliphatic ring in which one, two or more are substituted with substituents selected from the group consisting of a hydroxyl group and a halogen group; R is an aromatic ring substituted with a halogen group; or an aliphatic ring substituted with a halogen group; and Z is a trivalent organic group.
 12. The polymer electrolyte membrane of claim 1, which has ion conductivity of greater than or equal to 0.01 S/cm and less than or equal to 0.5 S/cm.
 13. The polymer electrolyte membrane of claim 1, which has an ion exchange capacity (IEC) value of 0.01 mmol/g to 5 mmol/g.
 14. The polymer electrolyte membrane of claim 1, which has a thickness of 1 μm to 500 μm.
 15. The polymer electrolyte membrane of claim 1, which is a reinforced membrane further including a substrate.
 16. A membrane-electrode assembly comprising: an anode; a cathode; and the polymer electrolyte membrane of claim 1 provided between the anode and the cathode.
 17. A polymer electrolyte-type fuel cell comprising: two more of the membrane-electrode assemblies of claim 16; a stack including a bipolar plate provided between the membrane-electrode assemblies; a fuel supplying unit supplying fuel to the stack; and an oxidizer supplying unit supplying an oxidizer to the stack.
 18. A redox flow battery comprising: a positive electrode cell including a positive electrode and a positive electrode liquid electrolyte; a negative electrode cell including a negative electrode and a negative electrode liquid electrolyte; and the polymer electrolyte membrane of claim 1 provided between the positive electrode cell and the negative electrode cell. 